Comparison of methods for determination of glomerular filtration rate in hypertensive subjects with normal serum creatinine.

BACKGROUND

Glomerular filtration rate (GFR) measured through technetium-99m diethyl triamine penta-acetic acid (Tc(99m)DTPA) renal scintigraphy (rsGFR) was compared with that estimated (eGFR) from 24-h creatinine clearance (CrCl) and, using both the Cockcroft-Gault (CG) and Modification of Diet in Renal Disease (MDRD) formulas, in a population of hypertensive subjects (HTs) with normal serum creatinine (SCr) levels.

PATIENTS AND METHODS

In 200 normoalbuminuric (<30 mg/24 h) HTs 55-75 years old, without diabetes and history of coronary and cerebrovascular diseases, Pearson's correlation assess the relationship between rsGFR and eGFR. The Bland-Altman method was used to assess the agreement between rsGFR and eGFR, separately in subjects with low (<60 ml/min/1.73 m(2)) and normal (≥60 ml/min/1.73 m(2)) rsGFR. The span between -1.96 and +1.96 standard deviations of mean difference (bias) was calculated and used for this purpose.

RESULTS

In 76 subjects, an unknown low renal function was found by Tc(99m)DTPA renal scintigraphy. In subjects with normal rsGFR the Bland-Altman analysis showed that the smallest span between rsGFR and eGFR was evident for ClCr values (26.0 ml/min/1.73 m(2)), whereas higher values were detected with the CG and MDRD formulas (41.0 and 40.4 ml/min/1.73 m(2), respectively). The same results were observed for low rsGFR, where a smaller span was found for ClCr (21.2 ml/min/1.73 m(2)), whereas CG and MDRD methods gave greater results (30.4 and 31.8 ml/min/1.73 m(2) respectively); no differences were found between genders. The degree of agreement for eGFR estimated with the CG and MDRD formulas was wider than that derived from ClCr, reflecting a greater between-methods variability and a considerable discrepancy of rsGFR values in the former than in the latter.

CONCLUSIONS

In HTs with normal SCr values, Tc(99m)DTPA renal scintigraphy discovered un known renal organ damage in 38% of cases. If this methodology is not available, ClCr measurement should be preferred to estimate GFR whereas CG and MDRD formulas are of limited efficacy.